I have a 4x4x1.5 grow cab with two Easy Riders growing in there. The smell was overpowering and filled the whole basement and first floor with smell. I put one of the True Air filters inside the cabinet and one outside the exhaust duct. In a matter of hours the smell was gone from the entire house. I really didn't have high hopes for them, but they perform really well for my needs. I know this thread's a little old, but I wanted my review out there so other people could use it to guide their decisions.